The present invention concerns a seating for a valve, a flow control outlet, or the like, comprising electrodes, specifically for use in detecting flaws in a layer of enamel, currently known as an xe2x80x9cenamel-testxe2x80x9d.
The seating according to the invention is preferably intended for the waste valve of a reactor, a tank, a column, or other container having an interior coating of enamel which must be tested for defects.
In the chemical industry it is sometimes necessary to utilize or store reagents or products that are particularly acidic or corrosive, making it impossible to use reactors, tanks, columns or other conventional containers with steel walls that would be attacked and deteriorate.
One solution in these cases is to use reactors or other containers with interior walls that are coated with a protective layer of enamel. This highly resistant, inert coating ensures that the reactor or container will be protected from corrosion by the contents.
However, to eliminate both the risk of container deterioration and the risk of leaks potentially dangerous to humans, equipment and the environment, the integrity of this protective coating must be assured at all times.
There must be a permanent means of controlling the condition of enamel layer. To do this, manufacturers use devices which detect flaws in the enamel layer, currently called xe2x80x9cenamel-testsxe2x80x9d.
To detect any possible enamel flaws, such a device must have three electrodes, one of which is connected to the metal mass of the container to be checked and the two others in contact with the liquid inside the container.
The two electrodes in contact with the liquid measure a reference current between them, which allows the conductivity of the liquid inside the reactor to be checked. To verify the continuity of the enamel layer, this device is used to measure the intensity of the current existing between the unit of these two electrodes and the metal mass of the reactor, using the third electrode. If there is a flaw in the enamel, a current leak is detected, which is proportionate in intensity to the area of the non-enameled surface.
Such a device allows simple, continuous verification of the integrity of the enamel layer. Possible flaws can be detected very early, thus preventing them from becoming worse or causing dangerous leaks, and making repairs easy and inexpensive.
To verify the integrity of the enamel coating, the two electrodes in contact with the liquid must be positioned as low as possible in the container to be controlled. For this reason, they are generally placed near the waste valve, which is obviously at the lowest point on the container.
According to the prior art, these electrodes are integral with the upper surface of the block on the piston of the waste valve, with the piston being movable between an upper position and a lower position, respectively corresponding to the open and closed valve positions. The wire conductors connecting these electrodes to the xe2x80x9cenamel-testxe2x80x9d. apparatus pass through the piston rod in the usual way.
Since the piston of the waste valve is in permanent contact with the corrosive environment inside the container, it must also be coated with protective enamel. Specific conductive materials must be used for this enamel layer, with a dilatation coefficient compatible with that of the enamel and similar chemical resistance, when constructing electrodes to be integrated within the upper surface of the piston head.
These electrodes are generally made of platinum or iridium when platinum is not sufficiently resistant to the corrosive action of the reactive environment. Therefore, these electrodes are rather expensive due to the use of these materials and their complex construction.
Moreover, if there is a problem with these electrodes or in the piston enamel, which is the reactor portion most frequently exposed to various forces (abrasion, mechanical shock, etc.), then it becomes necessary to change the entire blocking piston. Since this piston is completely enameled, it is quite expensive.
The object of the invention is to propose a device with integrated electrodes that is less expensive, easily replaceable, and which can be used in an enamel-coated container equipped with an xe2x80x9cenamel-testxe2x80x9d device.
To resolve this technical problem, the invention proposes a valve seating comprising at least one electrode and preferably two, which may either be attached to or integrated within said seating. These electrodes may be used, for example, inside a device that controls the integrity of an enamel coating such as an xe2x80x9cenamel-testxe2x80x9d device, but they are not limited to such a use.
The valve seating according to the invention is made using a fluoridated polymer, such as a TEFLON(copyright)-coated material, preferably solid glass-coated TEFLON(copyright) or reinforced TEFLON(copyright). This makes it resistant to the aggressive environment and because it is flattened, it forms a tight seal when the piston stop, in the lowered position, contacts it.
Each of the electrodes is made of conductive material compatible with the material of the valve seating so that it can either be attached to the body of the valve seating or integrated within it. Thus, it is preferably, but not necessarily, made of graphite TEFLON(copyright). The cost of such an electrode, perfectly adapted to the most corrosive environments, is considerably lower than a platinum or iridium electrode inserted into the piston enamel.
Furthermore, if there is a problem requiring electrode replacement, the valve seating of the invention can be quickly and easily dismounted and reattached by removing and replacing the valve without having to remove the piston from it. Since it is not enameled but made from a fluoridated polymer, the valve seating of the invention is economical, certainly much less expensive than an enameled piston.
The valve seating according to the invention may be used in conjunction with a device for regulating the condition of an enamel coating of the xe2x80x9cenamel-testxe2x80x9d type, although it is not limited to this use.
The seating of the invention is placed on the waste valve of the container to be checked in the lowest possible position for complete regulation. It comprises two electrodes, preferably in the form of conductive contact studs extending from the upper wall of the seating so as to contact the container.